Radiology departments contribute substantially to a hospital's carbon footprint and the modality with the worst record is typically MRI. The electrical energy consumed by a scanner ends up as waste heat in its internal cooling-water circuit, and additional money and energy are normally spent to dispose of that waste heat (such as via a secondary house cooling circuit). Attempts to re-use this heat are rarely made, arguing that the cooling water's temperature level would be too low and the heat flow too volatile for secondary use. Here, we report a do-it-yourself approach to waste-heat recovery, which was implemented in February 2024, a few months after a new 3T scanner (Cima.X; Siemens Healthineers) was installed at our site.
The power consumption of the scanner in various states of idleness was measured with a power meter (PQA 435; Fluke Corporation) at the circuit breaker panel, yielding 27.5 kW in “scanner ready,” 11.1 kW in “eco,” 7.4 kW in “stand-by,” and 5.5 kW in “sleep” mode. In eco mode, which is entered automatically, the gradient power amplifiers are turned off, and the system's two internal water pumps are slowed down. In stand-by mode, which must be entered manually, everything is shut off except the He compressor (5.7 kW) and the water pumps (1.7 kW). In sleep mode, entered automatically, the He compressor cycles between 8-min on and 4-min off states, reducing its average power consumption to 3.8 kW. These 3.8 kW were targeted for recovery, as this heat is available 24/7 and comes at a relatively high temperature level of 30ºC or 36°C, depending on the pump speed.
Figure 1A shows a schematic of the original hydraulic components. In the scanner's cooling circuit, the return water from all system components is collected in one common pipe and then pumped through the heat exchanger (HE-1) with the house cooling circuit. A motor-controlled bypass valve keeps its outflow temperature at the target value of 24°C. Air flow and temperature in our 1402MRI building are controlled independently by a site-installed cabinet (ASU-300-CW; Stulz) equipped with an electrical heater and a water-to-air heat exchanger (HE-2) for cooling.
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Zitierung
Brühl, R., Dillinger, H., Trepte, D., & Ittermann, B. (2025). A do‐it‐yourself approach to waste‐heat recovery in MRI. Magnetic Resonance in Medicine, 1–2. https://doi.org/10.1002/mrm.70016
